Subject: Re: species concepts (was VCR Fox Sparrows)
Date: Jun 16 15:40:48 1995
From: "David B. Wright" - wrightdb at pigsty.dental.washington.edu


It is not clear that all named subspecies of North American=20
birds would in fact make good PSC species. Apparently many=20
subspecies lack diagnostic characters and would=20
not be recognized as PSC species. Note that Zink'=92s analysis=20
did not find that every named Fox Sparrow [or Song Sparrow?]=20
subspecies is a contender for being a PSC species. Note=20
also that Zink'=92s version of the PSC in recent papers is=20
toned down a lot from his position in McKittrick and Zink=20
1988 (i.e., not as fervid). In one of his talks here, Zink indicated=20
that he and a few other PSC types independently evaluated the same set=20
named bird species and found much agreement in which populations were=20
PSC species, and that on average each currently named species represented=
=20
about 2 PSC species (I think it was 2; did anyone take notes? Chris?).

Much of the movement toward the PSC is in a sense movement=20
*away from* the BSC. There are serious problems with the=20
BSC, *even if* one regards reproductive isolation as the=20
sine qua non of speciation. The "potential interbreeding"=20
criterion of the BSC lumps populations together on the=20
demonstrably flawed basis of simple similarity. The=20
hybridization criterion of the BSC incorrectly diagnoses=20
sister groups: populations are implicitly assumed to be=20
sister groups if they hybridize; New World orioles and=20
chickadees provide examples of the failure of this=20
criterion. (Presumably this is the basis for the rumored=20
unlumping of Baltimore and Bullock's orioles). =20

But a strict PSC has its problems, too. And there are other species=20
concepts to consider. For example, Ed Wiley's=92 Evolutionary Species
Concept, which is based on evolutionarily independent lineages, is in=20
some ways intermediate to the PSC and BSC (though closer to=20
the PSC). =20

David Wright
dwright at u.washington.edu